ИСТИНА

Nowadays amine-boranes (R1xNH(3-n)BH(3-y)R2y; R1,R2 = Alkyl, Ph) are considered as perspective materials for reversible hydrogen storage systems due to high H2 volumetric and gravimetric density of these compounds. They are isoelectronic to alkanes and could be used as a model of C-H bond activation in organometallic complexes with alkanes. Amine-boranes as well as other BNH bifunctional compounds containing both an acidic and basic group are capable to hydrogen evolution at heating due to existence BHδ−•••+δHN dihydrogen bonds (DHB) between acidic and basic functional groups. For Acid-base properties of the compounds (NH3BH3 (AB), (CH3)3CNH2BH3 (t-BuAB), (CH3)3NBH3 (TMAB) and (CH3)2NHBH3 (DMAB)) the interactions with a number of proton donors and organic bases were studied by VT-FTIR spectroscopy. This method is successfully used for studying the majority of organometallic compounds including metal and boron hydrides and hydrogen bonds. Through the hydrogen bond (HB) formation acids with BH and bases with NH in the IR spectra low-frequency shifts of the stretching vibrations of NH and OH groups were observed. Using the displacements values of the vibration frequencies the thermodynamic characteristics of HB complexes were determined (−ΔH° = 0.7 − 4.9 kcal/mol). By Iogansen rule of factors (ΔH = ΔH11•Pi•Ej) the acidity and basicity factors were determined. The acidity factor Pi(NH) is 0.26 (AB) < 0.51 (DMAB) ≈ 0.52 (t-BuAB) The basicity factor Ej(BH) is 0.61 (TMAB) ≈ 0.60 (DMAB) < 0.80 (t-BuAB) < 0.98 (AB). The kinetic of acid-mediated solvolysis of DMAB was studied in CH2Cl2 and acetone. HB complexes (intermediates of the reaction) were characterized by FTIR. The reaction products (B(OH)3 and B(OR)4 − and R4N+) were isolated and characterized by X-ray. The obtained results reveal the important role of intermolecular interactions in chemistry of amine-boranes. The existence of multiple DHB in its structure provides easier hydrogen releasing.